Last week, Microsoft Power BI’s privacy level descriptions were revised.
Previously, Microsoft documentation implied that the data protection firewall imposed unilateral, bidirectional isolation between data sources having incompatible privacy levels. In actuality, the direction of data flow is factored in when determining whether data folding can take place between sources. Privacy level documentation now reflects this.
Imagine a public-level and a private-level data source that are joined together. The old privacy level descriptions incorrectly stated that a privacy level private source would be isolated from all other sources, implying that data would not be allowed to fold from the private level source to the public level source or vice versa. In actuality—and as the revised documentation now reflects—data from a private level source won’t be folded into a public level source, but the public source’s data can be freely folded to a private source. So, in this scenario, folding can happen public -> private, just not private -> public.
| Privacy Level | Old Description | Revised Description |
| Private | A Private data source contains sensitive or confidential information, and the visibility of the data source may be restricted to authorized users. A private data source is completely isolated from other data sources. | A Private data source contains sensitive or confidential information, and the visibility of the data source may be restricted to authorized users. Data from a Private data source will not be folded to other sources (not even to other Private sources). |
| Organizational | An Organizational data source limits the visibility of a data source to a trusted group of people. An Organizational data source is isolated from all Public data sources, but is visible to other Organizational data sources. | An Organizational data source limits the visibility of a data source to a trusted group of people. Data from an Organizational data source will not be folded to Public data sources, but may be folded to other Organizational data sources, as well as to Private data sources. |
| Public | A Public data source gives everyone visibility to the data contained in the data source. Only files, internet data sources, or workbook data can be marked Public. | A Public data source gives everyone visibility to the data contained in the data source. Only files, internet data sources, or workbook data can be marked Public. Data from a Public data source may be freely folded to other sources. |
Again, to emphasize: Power BI has not changed behavior; rather, these documentation revisions correct the written privacy level descriptions so that they accurately describe Power BI’s existing behaviors.
These behaviors are good—better than the previously incorrectly documented behaviors. It is desirable and appropriate for data to be folded from less sensitive sources into more sensitive sources (but, of course, not the other way around).